The present invention, in some embodiments thereof, relates to a method and system of cancelling interferences in RF communication systems, such as, for example, self interferences occurring in collocated transceivers configurations and antennas pattern partial overlap interferences (also referred to herein as cross lobe interferences).
For example, wireless networks relay base-stations (BSs) are often used to connect remote subscriber-stations (SSs) to the wireless network over a wireless backhaul link that is typically operating within the same frequency band or frequency block used by the relay BS to communicate with the SSs. The backhaul communication is carried out between the relay BS and another BS (typically a wired BS of a larger size) or a backhaul feeder system. Such relay BS with in-band backhaul link is also referred to herein as SBBS (Self Backhaul Base Station), which is a BS, or access point, that provides access to SSs and further maintains a backhaul link within the same spectral band or block.
The feeder BS, or backhaul feeder, which provides the backhaul payload to the SBBS, will be referred to hereinafter as MaBS (Macro Base Station), which may be a part of a wireless access network supporting communication to both backhaul (to SBBSs) and to SSs. Alternatively, the MaBS may be a backhaul feeding unit supporting only backhaul communication to SBBSs. The SBBS typically comprises a Micro BS (MiBS) transceiver used to communicate between the SBBS and SSs, and a Backhaul Subscriber Station (BHSS) transceiver used for communicating between the SBBS and the MaBS.
In many cases the antennas of the MiBS and the BHSS transceivers are adjacently located (e.g., distances of about 0.05 to 2 meters in cases of single enclosure or compact installation site). Under any network duplexing regime, time-division duplexing (TDD) or frequency-division duplexing (FDD), the BHSS transceiver of the SBSS may transmit communication signals concurrently (i.e., at the same time and using the same frequency band) during time periods in which the MiBS transceiver is in receive mode, tuned to the same (or neighboring) frequency of the transmitter, and vice versa. This situation causes major difficulties, as the antennas of the MiBS and BHSS are located in close proximity, where one antenna is transmitting and the other antenna is receiving, and both transceivers use the same (or close) frequency band in the same frequency block. As a result, interferences are typically introduced in signals received in antennas of both BHSS and MiBS receivers, which hamper the quality of service (QoS) and the extent of potential capacity of both the backhaul and access links.
It is noted that such interferences also occur when the collocated transceivers are not using the same frequency channel, but are still using the same spectrum block (or band). Usually transmitters and receivers that can be tuned to any frequency channel within the spectrum block are not equipped with screening filters in their front RF stages, as the actual filtering is typically performed further in the RF chain. Thus, the strong interfering signal in the same spectrum block will hamper the communication link, which may cause saturation in the receiver's front RF stages that cannot be corrected later in the digital baseband signal processing. Such strong interferences may enforce lower gain of the low noise amplifier (LNA) attempting to avoid saturation in the receiver front end circuit, which may hamper the whole link performances of both collocated transceivers.
Interference may be also caused by transmitter deficiencies that may result in out-of-band, or in-band, output noise. This out-of-band, or in-band, transmitter noise may be so strong within the receiver's band such that it may hamper the desired signals.
Interference in reception of a desired signal may also occur when the receiving antennas of the desired signal and of the transmitting antenna of the interfering signal are not collocated i.e., when the desired signal receiving antenna is remotely located relative to location of interfering signal transmitting antenna. For example, interference in reception of a remotely located desired signal receiving antenna may occur in the following cases:                A. When there is collocation and overlap between the desired signal transmitting antenna patterns and the interfering signal transmitting antenna patterns; and/or        B. When there is collocation and overlap between desired signal receiving antenna patterns and the interfering signal receiving antenna patterns.        
Such interference between collocated overlapping antenna patterns typical occurs in backhaul feeder implementations, when the same frequency band is used for the communication of a plurality of SBBSs.